Is there a quick way to unwrap an image texture onto a complex mesh?
I downloaded the file myself and checked, the folder contained another zip file in the source folder with the fbx and textures, those i used. The png files in the texture folder seem no different, except their size due to the file-format, up to you which you wanna use.

In Blender, after importing, the last object in the outliner (marked red in the picture) got a new material and i used the Albedo, Roughness, Metallic and Normal textures as "Image Texture" nodes.
The use of the "Texture Coordinate" and "Mapping" nodes are not needed for this to work, just used to use them. Added a picture to show that it's working even without the "Mapping" node.

The uv-coordinates are fine and all there. The textures align as well.
The picture shows the Object with it's textures applied.